The Kriegsmarine was the navy of Nazi Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war Reichsmarine (1919–1935) of the Weimar Republic. The Kriegsmarine was one of three official branches, along with the Heer and the Luftwaffe, of the Wehrmacht, the German armed forces from 1935 to 1945.
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare role and enforcing a naval blockade against enemy shipping. The primary targets of the U-boat campaigns in both wars were the merchant convoys bringing supplies from Canada and other parts of the British Empire, and from the United States, to the United Kingdom and to the Soviet Union and the Allied territories in the Mediterranean. German submarines also destroyed Brazilian merchant ships during World War II, causing Brazil to declare war on both Germany and Italy on 22 August 1942.
A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support. It may also be used in a non-military sense, for example when driving through remote areas. Arriving at the scene of a major emergency with a well-ordered unit and intact command structure can be another motivation.
Q-ships, also known as Q-boats, decoy vessels, special service ships, or mystery ships, were heavily armed merchant ships with concealed weaponry, designed to lure submarines into making surface attacks. This gave Q-ships the chance to open fire and sink them. The use of Q-ships contributed to the abandonment of cruiser rules restricting attacks on unarmed merchant ships and to the shift to unrestricted submarine warfare in the 20th century.
The Battle of the Atlantic, the longest continuous military campaign in World War II, ran from 1939 to the defeat of Nazi Germany in 1945, covering a major part of the naval history of World War II. At its core was the Allied naval blockade of Germany, announced the day after the declaration of war, and Germany's subsequent counter-blockade. The campaign peaked from mid-1940 through to the end of 1943.
USS Leary (DD-158) was a Wickes-class destroyer in the United States Navy during World War II. She was named for Lieutenant Clarence F. Leary, posthumously awarded the Navy Cross in World War I.
The first USS Warrington (DD-30) was a modified Paulding-class destroyer in the United States Navy during World War I. She was named for Lewis Warrington.
USS Parker was an Aylwin-class destroyer built for the United States Navy prior to the American entry into World War I. The ship was the first U.S. Navy vessel named in honor of Foxhall A. Parker, Jr., a U.S. Navy officer who served in the American Civil War, and as Superintendent of United States Naval Academy.
The first USS McCook (DD-252) was a Clemson-class destroyer in the United States Navy. Entering service in 1919, the ship had a brief active life before being placed in the reserve fleet. Reactivated for World War II, the ship was transferred to the Royal Navy and then to the Royal Canadian Navy and renamed HMCS St. Croix. Assigned as a convoy escort in the Battle of the Atlantic, St. Croix was torpedoed and sunk on 20 September 1943.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, and/or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
The Battle of the Caribbean refers to a naval campaign waged during World War II that was part of the Battle of the Atlantic, from 1941 to 1945. German U-boats and Italian submarines attempted to disrupt the Allied supply of oil and other material. They sank shipping in the Caribbean Sea and the Gulf of Mexico and attacked coastal targets in the Antilles. Improved Allied anti-submarine warfare eventually drove the Axis submarines out of the Caribbean region.
USS Henry R. Mallory (ID-1280) was a transport for the United States Navy during World War I. She was also sometimes referred to as USS H. R. Mallory or as USS Mallory. Before her Navy service she was USAT Henry R. Mallory as a United States Army transport ship. From her 1916 launch, and after her World War I military service, she was known as SS Henry R. Mallory for the Mallory Lines. Pressed into service as a troopship in World War II by the War Shipping Administration, she was torpedoed by the German submarine U-402 in the North Atlantic Ocean and sank with the loss of 272 men—over half of those on board.
SS El Occidente was a cargo ship for the Morgan Line, a subsidiary of the Southern Pacific Company. During World War I, she was known as USAT El Occidente in service with the United States Army and as USS El Occidente (ID-3307) in service with the United States Navy. At the end of war, she reverted to her original name of SS El Occidente.
SM U-117 was a Type UE II long-range minelayer submarine of the Imperial German Navy. She was laid down in 1917, at Hamburg, Germany, by Aktiengesellschaft Vulcan and launched on 10 December 1917. She was commissioned in the Imperial German Navy on 28 March 1918, with Kapitänleutnant Otto Dröscher in command. After shakedown, U-117 was posted to the U-Kreuzer Verband on 1 June 1918. Over the next five weeks, she completed fitting out at Kiel.
The U-boat Campaign from 1914 to 1918 was the World War I naval campaign fought by German U-boats against the trade routes of the Allies. It took place largely in the seas around the British Isles and in the Mediterranean. The German Empire relied on imports for food and domestic food production and the United Kingdom relied heavily on imports to feed its population, and both required raw materials to supply their war industry; the powers aimed, therefore, to blockade one another. The British had the Royal Navy which was superior in numbers and could operate on most of the world's oceans because of the British Empire, whereas the Imperial German Navy surface fleet was mainly restricted to the German Bight, and used commerce raiders and unrestricted submarine warfare to operate elsewhere.
The Atlantic U-boat campaign of World War I was the prolonged naval conflict between German submarines and the Allied navies in Atlantic waters—the seas around the British Isles, the North Sea and the coast of France.
The action of 8 May 1918 was a small naval engagement which occurred off Algiers, North Africa during World War I. In the action, an American armed yacht and a British destroyer encountered the German U-boat UB-70. Initially, the engagement was thought to be inconclusive, but later on the allied warships were credited with sinking the German submarine.
The action of 5 September 1918 was a naval battle 200 mi off the coast of France in the North Atlantic during World War I. The action was fought between a German U-boat and American warships.
The Torpedo Alley, or Torpedo Junction, off North Carolina, is one of the graveyards of the Atlantic Ocean, named for the high number of attacks on Allied shipping by German U-boats in World War II. Almost 400 ships were sunk, mostly during the Second Happy Time in 1942, and over 5,000 people were killed, many of whom were civilians and merchant marines. Torpedo Alley encompassed the area surrounding the Outer Banks, including Cape Lookout and Cape Hatteras.
United States Navy operations during World War I began on April 6, 1917, after the formal declaration of war on the German Empire. The American navy focused on countering enemy U-boats in the Atlantic Ocean and the Mediterranean Sea, while convoying men and supplies to France and Italy. Because of United States' late entry into the war, her capital ships never engaged the German fleet, and few decisive submarine actions occurred.
United States 
German Empire